Mesa (master): i965: Rework the unlit centroid workaround.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: 875341c69b99dea7942a68c9060aa31a459e93fc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=875341c69b99dea7942a68c9060aa31a459e93fc

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Mon Aug  1 20:59:08 2016 -0700

i965: Rework the unlit centroid workaround.

Previously, for every input, we moved the dispatch mask to the flag
register, then emitted two predicated PLN instructions, one with
centroid barycentric coordinates (for normal pixels), and one with
pixel barycentric coordinates (for unlit helper pixels).

Instead, we can simply emit a set of predicated MOVs at the top of
the program which copy the pixel barycentric coordinates over the
centroid ones for unlit helper pixel channels.  Then, we can just
use normal PLNs.

On Sandybridge:

total instructions in shared programs: 7538470 -> 7534500 (-0.05%)
instructions in affected programs: 101268 -> 97298 (-3.92%)
helped: 705
HURT: 9 (all of which are SIMD16 programs)

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
Reviewed-by: Matt Turner <mattst88 at gmail.com>

---

 src/mesa/drivers/dri/i965/brw_fs_nir.cpp     | 26 +---------------------
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 32 ++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index c1f413b..e1655a4 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -3422,31 +3422,7 @@ fs_visitor::nir_emit_fs_intrinsic(const fs_builder &bld,
          interp.type = BRW_REGISTER_TYPE_F;
          dest.type = BRW_REGISTER_TYPE_F;
 
-         if (devinfo->needs_unlit_centroid_workaround &&
-             bary_intrin == nir_intrinsic_load_barycentric_centroid) {
-
-            /* Get the pixel/sample mask into f0 so that we know which
-             * pixels are lit.  Then, for each channel that is unlit,
-             * replace the centroid data with non-centroid data.
-             */
-            bld.emit(FS_OPCODE_MOV_DISPATCH_TO_FLAGS);
-
-            fs_reg dest_i = offset(dest, bld, i);
-            fs_reg dst_xy_pixel =
-               delta_xy[brw_barycentric_mode(interp_mode,
-                  nir_intrinsic_load_barycentric_pixel)];
-
-            fs_inst *inst;
-            inst = bld.emit(FS_OPCODE_LINTERP, dest_i, dst_xy_pixel, interp);
-            inst->predicate = BRW_PREDICATE_NORMAL;
-            inst->predicate_inverse = true;
-            inst->no_dd_clear = true;
-
-            inst = bld.emit(FS_OPCODE_LINTERP, dest_i, dst_xy, interp);
-            inst->predicate = BRW_PREDICATE_NORMAL;
-            inst->predicate_inverse = false;
-            inst->no_dd_check = true;
-         } else if (devinfo->gen < 6 && interp_mode == INTERP_MODE_SMOOTH) {
+         if (devinfo->gen < 6 && interp_mode == INTERP_MODE_SMOOTH) {
             fs_reg tmp = vgrf(glsl_type::float_type);
             bld.emit(FS_OPCODE_LINTERP, tmp, dst_xy, interp);
             bld.MUL(offset(dest, bld, i), tmp, this->pixel_w);
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 6d84374..4e0db06 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -308,9 +308,41 @@ fs_visitor::emit_interpolation_setup_gen6()
    this->wpos_w = vgrf(glsl_type::float_type);
    abld.emit(SHADER_OPCODE_RCP, this->wpos_w, this->pixel_w);
 
+   brw_wm_prog_data *wm_prog_data = (brw_wm_prog_data *) prog_data;
+   uint32_t centroid_modes = wm_prog_data->barycentric_interp_modes &
+      (1 << BRW_BARYCENTRIC_PERSPECTIVE_CENTROID |
+       1 << BRW_BARYCENTRIC_NONPERSPECTIVE_CENTROID);
+
    for (int i = 0; i < BRW_BARYCENTRIC_MODE_COUNT; ++i) {
       uint8_t reg = payload.barycentric_coord_reg[i];
       this->delta_xy[i] = fs_reg(brw_vec16_grf(reg, 0));
+
+      if (devinfo->needs_unlit_centroid_workaround &&
+          (centroid_modes & (1 << i))) {
+         /* Get the pixel/sample mask into f0 so that we know which
+          * pixels are lit.  Then, for each channel that is unlit,
+          * replace the centroid data with non-centroid data.
+          */
+         bld.emit(FS_OPCODE_MOV_DISPATCH_TO_FLAGS);
+
+         uint8_t pixel_reg = payload.barycentric_coord_reg[i - 1];
+
+         set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                           bld.half(0).MOV(brw_vec8_grf(reg, 0),
+                                           brw_vec8_grf(pixel_reg, 0)));
+         set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                           bld.half(0).MOV(brw_vec8_grf(reg + 1, 0),
+                                           brw_vec8_grf(pixel_reg + 1, 0)));
+         if (dispatch_width == 16) {
+            set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                              bld.half(1).MOV(brw_vec8_grf(reg + 2, 0),
+                                              brw_vec8_grf(pixel_reg + 2, 0)));
+            set_predicate_inv(BRW_PREDICATE_NORMAL, true,
+                              bld.half(1).MOV(brw_vec8_grf(reg + 3, 0),
+                                              brw_vec8_grf(pixel_reg + 3, 0)));
+         }
+         assert(dispatch_width != 32); /* not implemented yet */
+      }
    }
 }